| 摘要 |
PURPOSE:To shield the electric field noise in a receiving mode and to suppress the field radiation in a transmitting mode, by forming a shielding conductor of a loop antenna which carries out a communication with a car on a road into such a structure in that the shielding coat is cut at a point symmetrical to the input side. CONSTITUTION:A loop antenna 1 put on a road is connected to a ground communication set and carries out a communication with an antenna 4 mounted on a car 3 and when the car 3 passes through the antenna 1. An antenna core wire 13 of the antenna 1 is covered with a shielding conductor 12. The conductor 12 is cut at a symmetrical point in terms of an antenna input part B, i.e. at point A where lenghts L1 and L2 are equal and furthermore connected electrically to a shielding conductor 14 of a cable 11 at the part B to be fixed at a specific potential. In such constitution, an induction of the electric field noise can be prevented in a receiving mode, and a radiation of unnecessary electric field can be suppressed in a transmitting mode. |
